Generally, the common input device such as a mouse or a keyboard is electrically connected with a computer through a universal serial bus (USB) interface. Consequently, the computer can provide electricity to the input device through the USB interface in order for powering the input device. In addition, the user can operate the input device to perform the input operation on the computer. For example, characters and symbols can be directly inputted into the computer through the keyboard. When the mouse is held by the user's palm and moved, the cursor shown on a display screen of the computer is correspondingly moved. Moreover, when the mouse is operated through the user's finger, the icon or the window shown on the display screen of the computer can be selected or scrolled.
For increasing the application and entertainment, an input device with a luminous function has been introduced into the market. For example, the input device with the luminous function includes a luminous keyboard or a luminous mouse. FIG. 1 is a schematic functional block diagram illustrating a portion of a conventional input device with a luminous function. The input device 1 comprises a USB interface 11, a red LED unit 12, a green LED unit 13, a blue LED unit 14, a microprocessor 15 and a driving circuit 16. The USB interface 11 is electrically connected between the computer 2 and the microprocessor 15. The driving circuit 16 is connected between the microprocessor 15, the red LED unit 12, the green LED unit 13 and the blue LED unit 14. The microprocessor 15 acquires electricity from the computer 2 through the USB interface 11. Consequently, the microprocessor 15 provides a first driving current I11, a second driving current I12 and a third driving current I13 to the red LED unit 12, the green LED unit 13 and the blue LED unit 14, respectively.
When the first driving current I11 is transmitted to the red LED unit 12 through the driving circuit 16, the red LED unit 12 emits a red light beam. When the second driving current I12 is transmitted to the green LED unit 13 through the driving circuit 16, the green LED unit 13 emits a green light beam. When the third driving current I13 is transmitted to the blue LED unit 14 through the driving circuit 16, the blue LED unit 14 emits a blue light beam. According to the practical requirements, the red light beam, the green light beam and the blue light beam may be mixed together. Consequently, the mixed light beam with a specified color can be outputted from the input device 1. For example, the mixed light beam is a white light.
However, the applications of the input device 1 with the luminous function are usually limited. For example, in case that the USB interface 11 is a USB2.0 interface, the input device 1 is only able to receive the operating voltage of 5V and the operating current of 500 mA. For allowing the input device to output the mixed light beam (i.e., the white light) of the red light beam, the green light beam and the blue light beam, the operating current of the input device 1 (e.g., 500 mA) is averagely split into the first driving current I11, the second driving current I12 and the third driving current I13. That is, the upper limit of the first driving current I11, the upper limit of the second driving current I12 and the upper limit of the third driving current I13 are approximately in the range between 150 mA and 170 mA. Consequently, the luminous intensity of the white light from the input device is usually insufficient.
As mentioned above, each of the upper limit of the first driving current I11, the upper limit of the second driving current I12 and the upper limit of the third driving current I13 is approximately in the range between 150 mA and 170 mA. In case that the input device 1 provides the red light beam only, the luminous intensity of the red light beam is insufficient. Similarly, in case that the input device 1 provides the green light beam only, the luminous intensity of the green light beam is insufficient. Similarly, in case that the input device 1 provides the blue light beam only, the luminous intensity of the blue light beam is insufficient. In other words, the light utilization efficiency of the conventional input device 1 is not satisfactory.
Moreover, the conventional input device 1 with the luminous function still has some other drawbacks. For example, the color of the output light is adjusted according to the red light beam from the LED unit 12, the green light beam from the green LED unit 13 and the blue light beam from the blue LED unit 14 only. Consequently, the adjusting flexibility of the color of the output light in the chromaticity coordinate is restricted. Especially when the output light is the white light, the adjusting flexibility is largely restricted. For allowing the white light to comply with the required white balance color temperature, it is necessary to simultaneously adjust the first driving current I11, the second driving current I12 and the third driving current I13. After many experiments and calibrations, the color of the output light from the input device 1 may reach the corresponding chromaticity coordinate.
In other words, the conventional input device needs to be further improved.